Democratic U.S. presidential candidate Hillary Clinton and her husband former U.S. president Bill Clinton wave at a campaign stop with Irish American supporters in the Manhattan borough of New York City MIKE SEGAR/REUTERS

Windmills are seen at dusk in Campo de Criptana, Spain, April 4, 2016. Locals believe that Miguel de Cervantes drew inspiration from the windmills of Campo de Criptana to narrate the battle between Don Quixote and the windmills he mistook for giants. SUSANA VERA/REUTERS

A Spanish fisherman stands on a beach while an outline of the Queen Elizabeth II is seen projected on the Rock of the British Colony of Gibraltar to celebrate her 90th birthday, from La linea de la Concepcion JON NAZCA/REUTERS

A prototype of the first Japan-made stealth fighter X-2 Shinshin, formerly called ATD-X, takes off to mark its maiden flight at Nagoya Airfield, also known as Komaki Airport, in Toyoyama town, Aichi prefecture KYODO/REUTERS

At dusk the blast furnaces are lit up at the now-closed Bethlehem Steel mill in Bethlehem, Pennsylvania, U.S. April 21, 2016. After Bethlehem Steel's blast furnaces went silent 20 years ago in the city of Bethlehem, Pennsylvania, the local economy bounced back as new industrial parks filled with e-commerce companies and white-collar businesses fleeing New York's higher costs. That adds to the challenge for Donald Trump, Republican nominee for the U.S. presidency, as he seeks voters' backing in the state's primary on April 26. BRIAN SNYDER/REUTERS

A refugee sits at the entrance of his tent following heavy rainfall at a makeshift camp for migrants and refugees at the Greek-Macedonian border near the village of Idomeni ALEXANDROS AVRAMIDIS/REUTERS

Children, who permanently live at the territory contaminated with radionuclides after the Chernobyl nuclear power plant accident, take physiotherapy while they are in a children's rehabilitation and health centre on the outskirts of Minsk VASILY FEDOSENKO/REUTERS

A pilot looks up from a U.S. F-22 Raptor fighter as it prepares to refuel in mid-air with a KC-135 refuelling plane over European airspace during a flight to Britain from Mihail Kogalniceanu air base in Romania TOBY MELVILLE/REUTERS